Conditions for pitting of high carbon steel

[Gem1]

I am having a reasonably severe pitting problem with high carbon(0.9%)low alloy steel. The steel is well coated in grease, but the water content of the roller grease is way above spec. I'm thinking that the water is a big part of the problem but am having trouble finding information about the conditions required for pitting in this type of steel.

Can anyone tell me the critical pH levels for pitting in a high carbon steel? Any other information about causes of pitting in a greased high carbon steel would be great too.

Thanks.

 

[CoryPad]

Ferritic steel is susceptible to pitting corrosion in alkaline chloride conditions. A typical pH would be ~ 9. The Cl^- concentration is the important part - you need to reduce or eliminate the source of this.

 

[metengr]

Gem1;
Have these rollers been placed in service? If so, are you sure this is corrosion and not macropitting?

 

[Gem1]

Thanks CoryPad. The rollers are martensitic, but this is still a good help.

metengr: Yes the rollers have been in service and there are macropitting issues too. However, I've done micros and am fairly sure the pitting is a corrosion issue. Significant pitting is seen on the non-running faces of the rollers too.

 

[CoryPad]

Martensitic will be the same as ferritic in this case.